1. Field of the Invention
The present invention relates to a method of reproducing text on a raster output device, such as a CRT screen, and to a raster output device implementing such method.
2. Description of Related Art
In order to achieve good readability of a text printed on paper or displayed on a CRT screen, it is essential that the blank spaces separating the individual words are readily perceptible, so that the reader may structure the text line into a sequence of words and may recognize the individual words by their overall appearance. In a given set of fonts with different font sizes, the width of the word-separating blanks is generally set in proportion to the average size of the characters, and the width ratio between the word-separating blanks and the white spaces between the individual characters within the word should be between 8:1 and 4:1.
In a raster output device, the image resolution is limited by the pixel size. If small font sizes, for example 9 point or smaller, are used on an ordinary CRT screen, the width of the word-separating blanks may become as small as 2 pixels. Since, however, the width of the white inter-character spaces within the words, the so-called character white, cannot become smaller than one pixel, the width ratio is reduced to 2:1, and it becomes more difficult to distinguish the word-separating blanks from the character white. In addition, the image resolution of the CRT-screen is not sufficient for reproducing all the details of the small font size characters which makes it more difficult to recognize the individual characters. Due to a combination of these effects, it becomes difficult to read the text fluently.
To alleviate this problem, one might think of increasing the word-separating blanks disproportionately, so that the width of these blanks may not become smaller than 3 pixels, for example. Then, however, the layout of the document would depend on the resolution of the raster output device with which it is reproduced. If, for example, a text which has been displayed on a CRT screen is printed with a laser printer which has a higher resolution than the CRT, the printed image would be different from the image shown on the screen, contrary to the so-called "What you see is what you get" (WYSIWYG) concept.